Collaboratively Answering Australia’s Geoscience Questions.

Deep seismic points the way to major mineral discoveries

A major seismic survey of deep continental crust in Western Australia has produced important clues to the potential location of world-class mineral deposits.

The survey is one of a series around Australia co-funded by AuScope in partnership with Geoscience Australia and geological surveys in a number of states.

Conducted in 2011, it covered a distance of 581 kilometres between two of the ancient building blocks of the Australian continent known as the Pilbara and Yilgarn Cratons. The blocks collided over one billion years ago and created an area of complex and mineral-rich geology known as the Capricorn Orogen.

Professor Brian Kennett of the Australian National University, said the region had puzzled government and private sector geologists for a long time.

In some parts we have world-class discoveries such as the iron ore mines of Pilbara, along with large gold and base metal deposits. But there are also large areas with little or no discovery, mainly due to the lack of outcropping rocks. This lack of knowledge about what lies under the first metre or so of the crust makes finding the next large mineral deposit much more difficult. He said it was widely agreed that Australia would benefit from a deep seismic transect to understand this region and its mineral potential.

Regions of colliding crust such as the Capricorn Orogen are also now accepted as the most likely location of world-class mineral deposits because they have very deep faults and other structures that can bring mineral-rich fluids to the surface. This survey changed some of the basic thinking about tectonics in this type of region. It also identified a number of mantle-scale structures that were previously unrecognised because they had little or no expression at the surface. Importantly, these structures are now seen to have a close association with known mineral deposits. With these new structures now identified, mineral explorers have important leads in the search for new giant orebodies.

One of the greatest endorsement of the value of deep seismic transect work is that private explorers are now paying government to conduct major surveys on their behalf. AuScopes funding was important to create a national perspective. The states cant invest outside their borders, but with co-investment from AuScope and its partners it was possible to take surveys across state boundaries and answer some important questions about the Australian continent.

Caption: Progress in seismic transects across Australia. The pink lines indicate seismic reflection profiling undertaken by Geoscience Australia and partners and the bold green lines the profiles co-funded by AuScope.